Parts List
The V4 Miniscope consists of a Rigid-Flex PCB, filter set, achromatic lens set, half-ball lens, electrowetting lens, and machined or printed body. Below outlines the details of each of these components. For details on options of how to purchase/produce these components, go to the Part Procurement page of this wiki.
The design files for the Miniscope housing and base plate can be found in the "Miniscope-v4-Body-Parts" folder of this repository. The files are saved as both Fusion 360 design files and as STL files. We generally suggest you have the 3 body parts of the Miniscope machined out of Delrin (see Part Procurement for more details) but we have also had a lot of success 3D printing them using the Formlabs Form3 printer and their black resin. We suggest the base plate be machined out of Aluminum but this can also be made out of plastic or 3D printed on a Form3 printer but will be slightly less supportive. These components have been designed to be modular, allowing researchers to swap them in and out depending on the features needed. Below is a description of these parts:
The Objective Module fits two 3mm diameter achromatic lenses along with an electrowetting lens. Combined, the optics of the Objective Module act similar to a table-top objective. If you are familiar with the V3 Miniscope, this lens stack replaces the 2mm diameter Objective GRIN lens previously used and has the added benefits of less chromatic aberration, larger FOV, longer working distance, and electronic focusing.
The Excitation Module holds the mount for the excitation LED, excitation filter, and attaches to the side of the Emission Module. It also acts as a cover plate for the dichroic in the Emission Module.
The Emission Module acts as the central body of the V4 Miniscope. It holds a dichroic, half-ball lens, and achromatic tube lens.
The base plate provides a rigid mount on the animal's skull for the Miniscope to attach to. It uses a 00-80 set screw to fix the Miniscope in place while imaging. It is important that the fit between the base plate and Miniscope is a slip fit with minimal gap. When the Miniscope is locked in place, the corner opposite the set screw should not make contact with the base plate. Instead the 2 side walls on either side of the corner make contact between the Miniscope and base plate and provide stable support.
There are two variants of the Miniscope V4 Base Plate:
- Variant 1 is designed to be used with the Objective Module as is. The advantage of Variant 1 is it is a simpler design an could result in a base plate 1mm smaller than Variant 2.
- Variant 2 is designed to be used with an Objective Module that has the Objective Module Sleeve mounted to it. The advantage of Variant 2 is the physical mounting of the Minsicope into the base plate is now Aluminum on Aluminum not Aluminum on plastic. In addition, Variant 2 can use a cone point set screw which will register the Miniscope in the base plate as the set screw is tightened.
The Objective Module Sleeve is an option Aluminum sleeve the can be press-fit or glued onto the bottom portion of the Objective Module. When added to the Objective Module you must use Variant 2 of the base plate. This sleeve along with a cone point set screw provides additional rigidity, repeat-ability, and longevity to the Miniscope mounting mechanism.
The Rigid-Flex PCB holds all the on-board electronics needed for the V4 Miniscope. It contains a U.FL coax connector, voltage regulators, serializer, CMOS imaging sensor, BNO055 head orientation sensor, microcontroller, excitation LED and driver, and electrowetting lens driver. If you need to do any soldering rework on this board, it should be baked at 120 degrees C for at least 2 hours before hand.
The KiCad, BOM, gerbers, and Pick and Place files are provided in this repository. More details can be found on the Rigid Flex PCB page.
The majority of the documentation for the V4 Minsicope is centered around imaging neural activity using GCaMP. That being said, by swapping out the LED and filter set, the Miniscope is capable of imaging most fluorophores. Most filter manufacturers can dice any of their filters to custom sizes, just remember the standard V4 Miniscope design was designed to work with 1mm thick filters. Thinner or thicker filters might require additional modification.
The excitation filter is a 4mm x 4mm x 1mm band-pass optical filter used to narrow the spectrum of the excitation LED. For exciting GCaMP's we suggest using:
- Vendor: Chroma
- Part Number: ET470/40x
- Note: Diced to 4mm x 4mm in size
The emission filter is a 4mm x 4mm x 1mm long-pass or band-pass optical filter used to block out any remaining excitation light from the imaging sensor. For imaging GCaMP's fluorescence we suggest using:
- Vendor: Chroma
- Part Number: ET525/50m
- Note: Diced to 4mm x 4mm in size
The dichroic is a 6mm x 4mm x 1mm filter used to reflect short, excitation wavelengths and pass longer, emission wavelengths. For imaging GCaMP's fluorescence we suggest using:
- Vendor: Chroma
- Part Number: T495lpxr
- Note: Diced to 6mm x 4mm in size
The V4 Miniscope uses all off the shelf lenses. The design no longer relies on an objective GRIN lens which improves abberations, field-of-view, working distance, customization, and removes any issues with procuring GRIN lenses.
Three achromatic lenses make up the majority of the optical imaging path. Two of these lenses are 3mm diameter lenses and sit in the Objective Module, the third is a 4mm lens in the Emission Module and acts as a focusing tube lens. By mix and matching the focal lengths of the two lenses in the Objective Module, a range of working distances and fields-of-view can be achieved. For more information on that visit the Lens Configurations page. Below outlines the standard configuration which achieves single cell resolution, ~1mm diameter FOV, and ~1mm working distance:
| Quantity | Vendor | Part Number | Description |
|---|---|---|---|
| 2 | Edmund Optics | 45-089 | 3mm diameter, 6mm FL achromat used in the objective module |
| 1 | Edmund Optics | 63-691 | 4mm diameter, 10mm FL achromat used in the emission module |
The electrowetting lens (EWL) provides electronic focal length adjustment controllable through the Miniscope DAQ Software. The range of focal length adjustment depends on the other optics used in the optical path. When using the standard V4 optical configuration, this EWL provides +/-200um of adjustment. The EWL can be purchased from multiple vendors.
- Manufacturer: Corning (Varioptics)
- Part Number: A-25H0
- Description: 2.5mm clear aperture electrowetting lens
The Half-ball lens is used to collect and de-focus the excitation light produced by the excitation LED. Without this lens, an image of the surface of the LED will form co-planar with the imaging plane.
Vendor: Edmund Optics Part Number: 47-269 Description: 3.0mm Diameter, N-BK7 Half-Ball Lens
Just like previous Miniscopes, the V4 Miniscope uses a 50Ohm coaxial cable for power, communication, and data. Any 50Ohm coax cable should work with the system but, in general, the thinner the cable, the shorter it must be. For a rough guideline: a 0.3mm diameter coax cable like cannot be longer than 5 ft, a 1mm diameter coax cable can likely function at lengths over 15 feet.
Our go-to coax cable for freely behaving experiments (with a good trade off between weight, size, flexibility, and robustness) is:
- Vendor: Cooner Wire (can be purchased at other places too)
- Part Number: CW8251
- Description: Coax cable. 36AWG 26/50SPC TRANSCUCENT PFA TO .016" NOM. O.D. 44AWG SPC SHIELD WITH .010" WHITE SILICONE RUBBER JACKET TO .045" NOM O.D.
For thinner cabling, mouser sells a 0.3mm diameter Molex coax cable that works well:
- Vendor: Mouser (others)
- Mouser Part Number: 538-50MCX-37
- Part Number: 100065-0023
- Description: Coaxial Cables 42AWG PFA, 50 OHM MICRO COAX, PER FT
The Rigid-Flex PCB has been designed to accept both a directly solder coax cable as well as a Hirose U.FL miniature coax connector. Since Rigid-Flex PCBs often need to be baked at 120 degrees C for a few hours before doing any soldering on them, we highly recommend using a connectorized coax cable instead of directly soldering one to the PCB. The advantage is a connectorized cable can be swapped out quickly if damaged. It is important to use the Hirose version of a U.FL connector as other manufacturers' connectors seem to not fit as snugly.
- Manufacturer: Hirose
- Vendor: Digikey, Mouser
- Part Number: U.FL-PR-SMT2.5-1(10)
- Description: RF Connectors / Coaxial Connectors U.FL SMT PLUG F CONTACT 50OHM
- Important Note: These connectors are not designed to be repeatedly connected and disconnected. We suggest you keep connecting/disconnecting to a minimum and treat the connector/cable as part of the V4 Miniscope, only swapping it out if the cable gets damaged.
Hirose sells other U.FL connectors that will also work, some that come already connected to a coax cable (flexibility of cable may not be great though).
One end of the coax cable will connect to the V4 Minsicopes, the other end needs to have an SMA connector so it can connect to the Minsicope DAQ Box. There are many ways of connectorizing a coax cable with an SMA connector but since you will likely be using thin, less standard coax cables, we have designed a simple PCB to help facilitate this connectoriztion. You can find the PCB here:
You will also need a side mount SMA connector:
Vendor: Digikey Part Number: CONSMA013.062-ND
You will need both M1 self-threading screws for assembling the Miniscope and 00-80 set screws for the base plate locking mechanism. These can be found from a lot of vendors but we suggestion using:
| Quantity | Vendor | Part Number | Description |
|---|---|---|---|
| 7 | McMaster Carr or similar | 96817a704 | Thread-Forming Screws for Thin Plastic 18-8 Stainless Steel, M1 Size, 3 mm Long |
| 1 | McMaster Carr or similar | 92311A051 | 00-80 Set Screw (For Base Plate Variant 1) |
| 1 | TBD | TBD | 2-56 cone point set screw (For Base Plate Variant 2 with Objective Module Sleeve) |
We glue/epoxy the Rigid-Flex PCB onto the Miniscope. While modifications can be made to mount the Rigid-Flex PCB with screws and/or brackets, glue/epoxy has worked well for us it can completely seal the image sensor area and can also be removed if replacing or repairing parts is needed. Generally try to avoid using Cyanoacrolate glues (super glues) as they can cause plastics to become brittle and out-gas a hazy coating over optical surfaces. That being said, Loctite 444 has worked well as long as it is allowed to cure in an open space for a few days. We suggest using the follow (slightly ordered by our preference):
- Gorilla 2 Part Epoxy, 5 Minute Set (or similar)
- UV curable optical glue (Norland 68)
- PCB potting epoxy
- 2 part general purpose epoxies
- Loctite 444 with compatible Accelorator
T2 Torx Screw Driver for M1 thread-forming screws:
- Vendor: McMaster
- Part Number: 52995A24
Filter paper or Kim Wipes